Syringes are used to inject medications, to aspirate body fluids, to provide vacuum, and to transfer fluids. Many complicated medical procedures can benefit from the ability to use a syringe with one hand so that the other hand can be used for other tasks. However, aspiration with a standard syringe is difficult and awkward using one hand, resulting in loss of fine control and power during aspiration. A new design of syringe that permits both injection and aspiration with one hand, yet maintains fine motor control and the strength necessary to generate high pressures and vacuums would be a major advance in syringe technology.
Syringes can both inject or aspirate, but occasionally it can be important to fix or lock the plunger relative to the barrel in order to prevent the plunger from either going into the barrel (inadvertent injection) or out (inadvertent aspiration). To prevent this, various locking plunger designs have been proposed. See, e.g., U.S. Pat. No. 4,386,606 Tretinyak; U.S. Pat. No. 4,890,626 Wang. These plunger locks are particularly valuable for providing aspiration and holding a vacuum during needle biopsy procedures. See, e.g., U.S. Pat. No. 5,830,152 Liang-Che Tan; U.S. Patent D411,882 Minasian; U.S. Pat. No. 5,891,052 Simmons; U.S. Pat. No. 4,791,937 Wang; U.S. Pat. No. 4,874,385 Moran; U.S. Pat. No. 5,957,864 Oosterhof Most of these provide constant vacuum and suction, rather than variable vacuum.
First attempts at one-handed aspiration to provide variable vacuum involved the use of an external apparatus which is integral with the syringe and allows the plunger to be advanced or retracted using squeezing motions of the digits using one hand rather than pulling motion using two hands (U.S. Pat. No. 3,990,446. Taylor; Jewel Dean Randolph. 1976. Hypodermic syringe for stabilized aspiration by one hand.). Other patents create essentially the same device (U.S. Pat. No. 5,582,595. 1996. Haber; Terry M., Smedley; William H. Aspirating syringe having a plunger guide for a reciprocating plunger assembly.), and some use an adapter which can be fitted on a conventional syringe (U.S. Pat. No. 5,135,511. Houghton; Frederick C. 1992 Assembly for aspirating tissue, including adapter for syringe.) Several US patents (U.S. Pat. No. 4,484,915. 1984. Tartaglia; John A. Medical syringe; U.S. Pat. No. 4,639,248. Schweblin; Jean-Denis. 1987. Syringe, U.S. Pat. No. 6,368,308 Nerney Apr. 9, 2002 Syringe having forward-mounted plunger control; U.S. Pat. No. 4,594,073 Stine, Charles R. Jun. 10, 1986. Aspiration Syringe holder; U.S. Pat. No. 4,967,762 DeVeris, James H. Nov. 6, 1990. Biopsy syringe with suction vent; U.S. Pat. No. 5,115,816. Lee, Peter F. May 26, 1992. Single-hand controlled fine needle aspiration device; U.S. Pat. No. 5,469,860 De Santis, Stephen A. Nov. 28, 1995. Fine needle aspiration cytology device syringe holder; U.S. Pat. No. 5,498,246 Deutchman, Mark E., Deutchman Arnold H. Mar. 12, 1996. Aspirator/injector device with palm engaging handle; U.S. Pat. Des. No. 337,821, Jul. 27, 1993. Tan, Henry K. Fine needle aspiration biopsy gun.) describe a syringe with an external slide which attaches to the plunger, permitting one-handed operation.
All of the above designs are completely different in that they utilize a single piston and a single plunger. In addition, the position of the index and middle fingers as well as the thumb, must be moved on these syringes when switching from the aspiration to injection mode, resulting in intraoperative instability. In addition, during the single handed aspiration using these devices, the barrel and needle advance beyond the index and ring finger (loss of a stable platform), creating major difficulties in control and localization of the needle and resulting in instability and unpredictability during procedures. The present invention (the reciprocating, thumb-operated, double-plunger syringe) completely obviates the above problems by providing a stable platform for both injection and aspiration with the index and middle fingers in a fixed position, with the only required movement being a lateral movement of the thumb to the reciprocating plunger.
Other patents describe more complicated two compartment syringes and double plunger syringes, but these are usually based on a single barrel and are intended to mix or administer two different substances (U.S. Pat. No. 3,685,514: Cheney; Paul E. 1972. Two Compartment Syringe; U.S. Pat. No. 5,188,616: Nadal; Guy. 1993. Syringe with double plunger.). Others describe double piston devices (U.S. Pat. No. 4,036,232: Genese Joseph Nicholas 1977. Aspiration device; U.S. Pat. No. 4,437,859: Whitehouse; Craig M., Cox; Nigel, Burt; Allan G., Snyder; Daniel R.: 1984. Hydraulic syringe drive.), either mechanically or hydraulically driven, for aspirating fluids or administering medications.
Only three previous patents describe the basic reciprocating syringe (U.S. Pat. No. 6,245,046 B1 Sibbitt, Wilmer L. Jr.: Reciprocating Syringes, Jun. 12, 2001, U.S. Pat. No. 6,962,576 B1: Reciprocating syringes. Sibbitt, Wilmer L. Jr. Issued Nov. 8, 2005, and U.S. Pat. No. 6,231,550 Laughlin, Joshua May 15, 2001 One-handed single grip position aspiration and injection syringe) with the Sibbitt patents being dominant in terms of filing priority. The reciprocating syringe is characterized by two plungers, plunger equivalents, or parallel longitudinal members that are mechanically bound together so that they move in a reciprocating (alternating) fashion, so that when one plunger goes up the other goes down by the use of a pulley system, gears, hydraulics, or other mechanisms upon flexion of the thumb (U.S. Pat. No. 6,245,046 B1 Sibbitt, Wilmer L. Jr.: Reciprocating Syringes, Jun. 12, 2001, U.S. Pat. No. 6,962,5766 B1: Reciprocating syringes. Sibbitt, Wilmer L. Jr. Issued Nov. 8, 2005). This permits the syringe to be operated with one hand for both injection and aspiration. The present invention comprises refinements in reciprocating syringe design, the conversion of conventional syringes to reciprocating syringes, methods of production of reciprocating syringes, and the specific application of plunger locks to reciprocating syringes and other improvements all of which have special implications for syringe based procedures.